RandR structures weren't getting recreated on regen as they are currently
created in the PreInit function which isn't called at that time. Fixed it by
re-creating them at regen time in the ScreenInit function.

This bug is about crashing of the X Server when the last application exits. You
appear to be reporting a totally different bug, of the DRI not reinitializing
after server regeneration. Re-closing -- please open a new bug if you aren't
experiencing the specific bug in this report.